fallout The precipitation to the earth of radioactive particles from the smoke and vapor ( produced by burst of an atomic weapon when ‘ the violence of the disturbance has subsided, After the detonation of a weapon, metallic oxide particles in the atomic cloud collide with particles of dirt (or with droplets of water as well as materia] from the bottom.) up in the rising column.. These particles or droplets become contaminated with radioactivity amd they gradually fall back to earth, sometimes after having been carried considerable distances downwind, film badge Radioactivity sensitive device worn to indicate amount of radiation received. fireball The luminous sphere of hot gases which form a few millionths of a second after detonation of an atomic weapon and immediately starts expanding and cooling, -In a nominal atomic bomb explosion, the ball of fire reaches a maximum radius of about 450 feet, firing system 1. For an implosion weapon, that portion of the weapon which, upon signal from the arming system, transforms and stores electrical energy, and, upon signal from the fuzing system, discharges this stored electrical energy to detonate the implosion system, This firing system will normally consist of the firing set, firing switch, load coils, load plates, detonator cables, other connecting cables, and structure, 2. For gun-assembly weapons, that portion of the weapon which receives a signal to ignite a pyrotechnic powder train, which in turn ignites the propellant, fission Although fission of heavy nuclei can be brought about in a number of ways, there is only one that is of importance for the practical release of nuclear energy: This is the fission initiated by neutrons. The reason is that the fission process is itself accompanied by the liberation of neutrons, so that a chain reaction with the continuous release of energy is possible, Three of the isotopes which can be used in a fission chain process are Uranium-233, Uranium-235, and 322 APWL{HO SWEH -2-003k aul, ( c